Pigmentary base product and process for making the same



No Drawing.

Patented Feb. 28, 19 33 UNITED STAT ES PATENT "OFFICE;

PIGMENTARYBASE PRODUCT AND Application filed April 5,

My invention concerns a material adapted to serve as the pigment-arybase for paints and particularly such paints as are suitable for use as rustproof coatings for iron and other objects and surfaces, and the process for the manufacturing the same. In particular my invention relates to a pigmentary base for which metallic lead either alone or inthe form of alloys with a largely preponderating lead content serves as the starting material.

The object of my invention is toprovide a new and improved material of this character, which has properties making it particularly suitable as abase for anti-corrosive paint purposes. My material is difierent II'lSiIIHCt-UI'Q from material obtained for instance in the atomization of lead by mechanical means, where the product, though finely divided, .consists so to speak of solid little drops. The structure of my product is on the contrary exceedingly porous and spongy, which brings about the important advantage that it is readily and perfectly penetrated by the ve hicles, such as linseed oil and other materials, used for the purpose of preparing paints therefrom. Furthermore thisspongy condition brings about a. strong capacity of reacting with the fatty acids set free, for instance, from linseed oil, during the process of drying and bvthis means facilitates theproduction of a dense film of paint and furnishes very favorable conditions during the aging of the same.

Another advantage of my improved prodnot is its extremely fine division, as the maximum size of the individual particles composing the same must not go above microns. Owing to this high degree of dispersion, the covering power of paints made by using it as a base, is much greaterthan that of ordinary paints.

As far as the chemical composition'of my product is concerned,'I am of the opinion that the same consists of a fine dispersion of lead in lead oxide, or a pyrosol of lead in lead oxide, wherein the lead oxide in the disperse system constitutes the exterior phase, which surrounds the highly dispersed lead.

In carrying out the processof producing rnoonss FOR MAKING THE SAME i927.v SeriatNo. 181,27

t I proceed in the followthat pigmentary bodies v of particular activity are obtained when lead alloys, the melting points of which are lower than that of pure lead, are used as starting materials in place of metallic lead. -These are slowly oxidized while being maintained at a temperature between the melting point of the alloy and tha t of pure lead. For instance,an alloy containing of lead, 1 3% of antimony, and 2% of tin may be used, and

vthis is introduced-into a furnace of the usual construction provided with a flat pan-shaped hearth, the interior of which must be adapted to be closed air-tight, so that a slight vacue um can -'be established therein. 'I then melt the said metallic material, either by means of electricity, gas, or in ner, so that the melte any other suitable mand material spreads out in a thin layerupon the hearth. Ithenestabdesired degree in the interior of the said furnace and by means of the,

lisha vacuum of the same cause air to be through a plurality drawn into the furnace of tuyeres located. .111 a suitable position above the melted bath; the outward ends of whichtuyeres are in com-o munication with the rior ends of the said air jets issuing from atmosphere. The intetuyeres are arranged in the said tuyeres impinge upon the sameand a vigorous motion of the air is inducedlocally.

The action of the air causes the formation of the pigmentrayproduct described above,

as a portion of the molten material oxidizes,

While the rest is finely-dispersed through the oxide,'the whole th mentioned above.

us forming the pyrosol It is of importance that the temperature of the molten bath be closely regulated and watched and for this purpose the color of the pigmentary body must be carefully observed. If the pigment assumes a yellowish color, the

temperature has been allowed to rise too high. 9 In that case the heating is cut down orthe amount of air sucked in is increased. The normal color which the pigment should have I is dark gray.

c When using an a 2 if T mentioned above, I have obtained good results by keeping, the temperature of the molten bath between 250 and 280 C.

As the pigmentary body forms on the surface of the molten bath, as stated above, it is carried away by the suction of the air. It is collected in any suitable manner, such for instance in a bag'plant similar to those used for the deposition of flue dust.

In the same ratio as the pigmentary prod not formed is sucked out of the furnace, fresh raw material is introduced therein so that the process becomes continuous.

p As stated above, the maximum size of the particles of the pigmentary body must not exceed 50 microns and material'coarser than that is removed by air separation. Some- What coarser material may be brought to the required degree of fineness by grinding in a ball mill or other suitable device. Residue too coarse for this treatment returns to the furnace for retreatment.

As the operation is carried out in a vacuum no poisonous lead dust can escape into the Work rooms and any leak is indicated by a rise in pressure.

Having thus described my invention What I claim asnew and desire to secure by Letters Patent is: a r

1. A pigmentary base of thecharacter described, comprisingthe product produced by the oxidation of a lead alloy containing substantially 85 percent lead, 13 percent antimony and 2 percent tin, said oxidation havingbeen carried out at a temperature between 250 C. and 280 C.

2. A process for the production of a pigmentary base of the character described, which consists in melting an alloy of lead containing at least percent lead and having a melting point below that of pure lead, and

oxidizing said alloy at a temperature between its melting point and the melting point of pure lead.

'3. A process for-the production of a pigmentary base of the character described, which consists in melting an alloy oflead containing substantially percentlead, 13 percent antimony, and 2 percent tin, and oxidizing said alloy at a temperature between 250 C. and 280 C. r

In testimony whereof, I have signed my name to this specification this twenty-third day of February, 1927. i V

- AXEL VIGGO BLOM. 

